A known slide door apparatus for a vehicle includes a guide rail extending in a front-rear direction, i.e., a longitudinal direction, of a vehicle and a connection member including a guide roller that is configured to roll on a path formed by the guide rail. A slide door is supported at a vehicle body via the guide rail and the connection member so as to open and close a door opening portion of the vehicle formed at a side surface of the vehicle body based on a longitudinal movement of the slide door along the guide rail.
In addition, the aforementioned guide rail may include a body-side guide rail formed at the side surface of the vehicle body and a door-side guide rail formed at an inner side surface of the slide door.
For example, a slide door apparatus for a vehicle disclosed in JP2003-335136A, which will be hereinafter referred to as Reference 1, includes a first body-side guide rail at a lower position than a window portion of the vehicle formed by the slide door, and a second body-side guide rail at a lower edge of the door opening portion. The slide door apparatus further includes first and second door-side guide rails at positions facing the first and second body-side guide rails.
The guide rail is normally formed at the vehicle body, however, the guide rail is also formed at the inner side surface of the slide door to improve arrangement flexibility of the guide rail and the connection member connected thereto. As a result, according to the slide door apparatus disclosed in Reference 1, a window frame of a window glass forming the window portion may be omitted.
According to the slide door apparatus disclosed in Reference 1, however, a possibility of decrease in rigidity for supporting the slide door (i.e., support rigidity) caused by arrangement change of the guide rail may not be fully eliminated. Such decrease of support rigidity become noticeable as swing or shaky movement of the slide door, which may lead to decrease in quality feeling of the slide door apparatus.
A need thus exists for a slide door apparatus for a vehicle which is not susceptible to the drawback mentioned above.